Fixes ceph volume restore to larger image than source

If a backup is restored to a volume that is bigger than the
backup itself, which could be the case if --volume-id is
supplied, we need the option to set extraneous extents to zero
i.e. set extents after those from the backup to zero.

Change-Id: I3c226b9e7429371f6cd9b9bd81071ff765712975
Fixes: bug 1225126
Merge "Fixes ceph volume restore to larger image than source"